Research 100,397 Religious aspects 92,154 Religion 57,178 Railroads 37,689 Relations 34,849 RU ebook 33,696 Race relations 30,208 Roads 28,355 Religious life 18,617 Rhetoric 17,905 Rules and practice 17,792 Rock music 17,372 Rehabilitation 17,050 Reference 16,735 Regional planning 14,672 Real property 14,355 RELIGION 12,509 Reading 11,752 Russian literature 11,527 Russian language 10,163 Rural conditions 10,111 Refugees 9,955 Registers of births, etc 9,726 Reformation 9,056 Readers 9,046 Racism 8,970 Rural development 8,431 Research papers 8,352 Religious life and customs 8,034 Regimental histories 7,957 Requisitions, Military 7,539 Rites and ceremonies 6,912 Reading (Elementary) 6,816 Renaissance 6,774 Religion and science 6,618 Romanticism 6,530 Religions 6,499 Recreation 5,851 Rivers, creeks, streams, etc 5,846 Renewable energy sources 5,492 Recherche 5,471 Representative government and representation 5,445 Remote sensing 5,407 Report writing 5,393 Revolutionaries 5,351 Risk management 5,253 Radio 5,149 Registration and transfer 5,108 Roman 4,829 Romance 4,778 Retail trade 4,723 Risk assessment 4,686 Revenge 4,682 Rating of 4,620 Relations extérieures 4,599 Revolutions 4,569 Rates 4,372 Rare books 4,206 Reproduction 4,113 Race identity 4,070 Robotics 4,004 Russian 4,003 Radicalism 3,995 Recruiting 3,980 Race discrimination 3,959 Refuse and refuse disposal 3,837 Rock musicians 3,833 Radiation 3,763 Recruiting, enlistment, etc 3,733 Religion and politics 3,720 REFERENCE 3,708 Reading comprehension 3,592 Retirement 3,550 Rivers 3,467 Religious education 3,461 Rezeption 3,452 Radiography 3,447 Reclamation of land 3,427 Rap (Music) 3,297 Recreation areas 3,272 Radioactive waste disposal 3,255 Robots 3,248 Russian poetry 3,209 Restoration movement (Christianity) 3,166 Reformed Church 3,121 Reliability 3,106 Recreational use 3,066 Romans 3,056 Regionalism 3,050 Revenue 3,035 Reorganization 3,031 Roman law 3,022 Radio broadcasting 2,968 Reconstruction (U.S. history, 1865-1877) 2,930 Rituals 2,917 Readers for new literates 2,909 Readers (Primary) 2,867 Riots 2,864 Recht 2,830 Remedial teaching 2,828